Method and system for mems devices with dual damascene formed electrodes

ABSTRACT

Methods and systems for MEMS devices with dual damascene formed electrodes is disclosed and may include forming first and second dielectric layers on a semiconductor substrate that includes a conductive layer at least partially covered by the first dielectric layer; removing a portion of the second dielectric layer; forming vias through the second dielectric layer and at least a portion of the second dielectric layer, where the via extends to the conductive layer; forming electrodes by filling the vias and a volume that is the removed portion of the second dielectric layer with a first metal; and coupling a micro-electro-mechanical systems (MEMS) substrate to the semiconductor substrate. A third dielectric layer may be formed between the first and second dielectric layers. A metal pad may be formed on at least one electrode by depositing a second metal on the electrode and removing portions of the second metal, which may be aluminum.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of, and claims priority to, U.S. patentapplication Ser. No. 15/182,172, filed Jun. 14, 2016, and entitled“METHOD AND SYSTEM FOR MEMS DEVICES WITH DUAL DAMASCENE FORMEDELECTRODES,” the entirety of which application is hereby incorporatedherein by reference.

FIELD

Certain embodiments of the disclosure relate to semiconductor devices.More specifically, certain embodiments of the disclosure relate to amethod and system for MEMS devices with dual damascene formedelectrodes.

BACKGROUND

Micro-electro-mechanical systems (MEMS) devices have become prevalent inelectronic devices in applications such as motion sensing, gyroscopes,and microphones, for example. Current MEMS packaging techniques areexpensive and complicated.

Further limitations and disadvantages of conventional and traditionalapproaches will become apparent to one of skill in the art, throughcomparison of such systems with the present disclosure as set forth inthe remainder of the present application with reference to the drawings.

BRIEF SUMMARY

A system and/or method for MEMS devices with dual damascene formedelectrodes, substantially as shown in and/or described in connectionwith at least one of the figures, as set forth more completely in theclaims.

Various advantages, aspects and novel features of the presentdisclosure, as well as details of an illustrated embodiment thereof,will be more fully understood from the following description anddrawings.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a diagram of a MEMS device with dual damascene formedelectrodes, in accordance with an example embodiment of the disclosure.

FIGS. 2A-2G illustrate process steps in forming the device of FIG. 1with dual damascene electrodes, in accordance with an example embodimentof the disclosure.

FIG. 3 illustrates another example embodiment of a MEMS device with dualdamascene formed electrodes, in accordance with an example embodiment ofthe disclosure.

FIGS. 4A-4D illustrate process steps in forming the device of FIG. 3with dual damascene electrodes, in accordance with an example embodimentof the disclosure.

DETAILED DESCRIPTION

Certain aspects of the disclosure may be found in a method and systemfor MEMS devices with dual damascene formed electrodes. Exemplaryaspects of the disclosure may comprise forming first and seconddielectric layers on a semiconductor substrate, where the semiconductorsubstrate comprises a conductive layer at least partially covered by thefirst dielectric layer; removing a portion of the second dielectriclayer; forming vias through the second dielectric layer and at least aportion of the second dielectric layer, where the via extends to theconductive layer; forming electrodes by filling the vias and a volumecomprising the removed portion of the second dielectric layer with afirst metal; and coupling a micro-electro-mechanical systems (MEMS)substrate to the semiconductor substrate. A third dielectric layer maybe formed between the first and second dielectric layers. A metal padmay be formed on at least one electrode by depositing a second metal onthe electrode and removing portions of the second metal, which maycomprise aluminum, for example.

The MEMS substrate may be electrically coupled to the semiconductorsubstrate via the metal pad, the at least one electrode, and theconductive layer. A first gap between the semiconductor substrate andthe MEMS substrate may be between a first electrode that does not have ametal pad and a standoff formed in the MEMS substrate. A photoresistlayer may be patterned on the second dielectric layer and form a cavityin the first and second dielectric layers exposing the conductive layer,where the cavity is adjacent to at least one of the electrodes. The MEMSsubstrate may be coupled to the metal layer. A first gap between thesemiconductor substrate and the MEMS substrate may be between theexposed conductive layer and the first surface of the MEMS substrate. Asecond gap between the semiconductor substrate and the MEMS substratemay be between an electrode and the MEMS substrate. A third dielectriclayer may be formed between the first and second dielectric layers, andmay comprise a high density plasma oxide located lateral to the firstmetal. The second dielectric layer may comprise a silicon-oxide-nitridematerial. The first metal, which may comprise tungsten, for example, maybe thinned using a chemical-mechanical polishing (CMP) process and maybe thinned until first metal is coplanar with a top surface of thesecond dielectric layer. The second dielectric layer may be removed.

In the described embodiments micro-electro-mechanical systems (MEMS)refers to a class of structures or devices fabricated usingsemiconductor-like processes and exhibiting mechanical characteristicssuch as the ability to move or deform. In the described embodiments, theMEMS device may refer to a semiconductor device implemented as amicro-electro-mechanical system. The MEMS structure may refer to anyfeature that may be part of a larger MEMS device. MEMS devices often,but not always, interact with electrical signals. MEMS devices includebut are not limited to gyroscopes, accelerometers, magnetometers,pressure sensors, microphones, and radio-frequency components. Siliconwafers containing MEMS structures are referred to as MEMS wafers.

A structural layer may refer to the silicon layer with moveablestructures. An engineered silicon-on-insulator (ESOI) wafer may refer toan SOI wafer with cavities beneath the silicon structural layer. A capwafer typically refers to a thicker substrate used as a carrier for thethinner silicon device substrate in a silicon-on-insulator wafer.

A MEMS substrate provides mechanical support for the MEMS structure. TheMEMS structural layer is attached to the MEMS substrate. The MEMSsubstrate is also referred to as handle substrate or handle wafer. Insome embodiments, the handle substrate serves as a cap to the MEMSstructure. Bonding may refer to methods of attaching, and the MEMSsubstrate and an integrated circuit (IC) substrate may be bonded using aeutectic bond (e.g., AlGe, CuSn, AuSi), fusion bond, compression,thermocompression, adhesive bond (e.g., glue, solder, anodic bonding,glass frit). An integrated circuit (IC) substrate may refer to asemiconductor (e.g., silicon) substrate with electrical circuits, forexample CMOS circuits. A package provides electrical connection betweenbond pads on the chip to a metal lead that can be soldered to a printedboard circuit (PCB). A cap or a cover provides mechanical protection tothe structural layer and optionally forms a portion of the enclosure.Standoff defines the vertical clearance between the structural layer andthe IC substrate.

Standoffs may provide electrical contact between the structural layerand the IC substrate. Standoffs may also provide a seal that defines anenclosure. A cavity may refer to a recess in a substrate. A chipincludes at least one substrate typically formed from a semiconductormaterial. A single chip may be formed from multiple substrates, wherethe substrates are mechanically bonded together. Multiple chips includesat least two substrates, wherein the two substrates are electricallyconnected, but do not require mechanical bonding.

FIG. 1 is a diagram of a MEMS device with dual damascene formedelectrodes, in accordance with an example embodiment of the disclosure.Referring to FIG. 1, there is shown CMOS-MEMS device 100 comprising CMOSsubstrate 130, a MEMS substrate 140, and MEMS cover 150. The MEMSsubstrate 140 may comprise cavities 141 and may be bonded to the MEMScover 150 with a thin dielectric film (such as silicon oxide, not shown)in between. In some embodiments, the MEMS substrate 140 comprises singlecrystal silicon or poly crystal silicon, for example. The MEMS substrate140 may be electrically coupled to the CMOS substrate 130 via the metalpads 123. The portions of the MEMS substrate 140 extending down to theCMOS substrate 130 may comprise standoffs 143.

The CMOS substrate 130 comprises metal pads 123, which may comprisealuminum, for example, although the disclosure is not so limited, as anysuitable contact metal may be used, such as gold, silver, aluminum,titanium, tungsten, platinum, and alloys thereof, or similar materials.The metal pads 123 may be formed as described further with respect toFIGS. 2A-2G, and may provide electrical connections between devices inthe MEMS substrate 140 and the CMOS substrate 130. The metal pads 123may be formed on a multi-layer structure on the CMOS substrate 130,which may comprise dielectric layers 101, 105, 109, 111, and 113.Conductive layer 107 may comprise top metals for the CMOS substrate 130and in an example scenario, may comprise metal that was deposited on thesurface of the dielectric layer 101 and the vias 103 and patterned toprovide electrical contact to various points on the CMOS substrate 130,thereby providing isolated electrical connectivity to devices andcircuits. The vias 103 provide vertical electrical interconnects throughthe dielectric layer 101 between devices in the CMOS substrate 130 andthe metal layer 107.

The dielectric layer 101 may comprise a passivation layer, for example,to protect and electrically isolate devices in the CMOS substrate 130,and may comprise silicon dioxide, silicon nitride, or similar material,for example. Similarly, the dielectric layer 105 is deposited over thedielectric layer 101 and the conductive layer 107. The dielectric layer105 may comprise silicon dioxide, for example, although other dielectricmaterials are possible, and may comprise a thicker dielectric layer thanthe other layers. In addition, the dielectric layer 109 may be on thedielectric layer 105, and may comprise silicon dioxide, for example. Thechoice of various dielectric layers may be made based on etchselectivity, density, and/or desired dielectric constant, for example.

The dielectric layer 111 may comprise a nitride material, for example,although the disclosure is not so limited, and may provide a surface onwhich the electrodes 121 are formed. The electrodes 121 may comprise asingle metal layer extending from the metal layer 107 to the top surfaceof the dielectric layer 111.

In an example scenario, a different dielectric material from thedielectric layer 111 may be used for the dielectric layer 113. Forexample, the dielectric layer 113 may comprise a high density plasma(HDP) oxide layer adjacent to the dielectric layer 111.

Starting from Engineering SOI wafers to form the MEMS substrate 140shown in FIG. 1, reactive ion etching (RIE) may be utilized to definesmall protrusions, the standoffs 143 on the MEMS substrate 140, whichdefines the distance (gap) between the devices in the MEMS substrate 140and metal pad 123 when the MEMS substrate 140 is bonded to the CMOSsubstrate 130. The standoffs 143 and the adjacent cavity 141 enabledifferent gap heights between the MEMS substrate 140 and the CMOSsubstrate 130. A hermetic seal ring which defines the MEMS cavity mayalso be defined by forming standoffs in a seal ring shape in the MEMSsubstrate 140.

The MEMS substrate 140 may comprise a structural layer and a devicelayer, where the structural layer comprises the movable structures andthe device layer comprises the electronic devices or functionality forthe movable structures. For example, the regions of the MEMS substratethat comprise the standoffs 143 that are not coupled to the CMOSsubstrate may have freedom to move up and down in response to somemechanical input, such as movement, thereby changing the gap between thestandoffs 143 and the electrodes 121, and thus changing the capacitancebetween them. This change in capacitance may be measured, therebysensing the mechanical input. The MEMS cover 150 may comprise aprotective structure for the MEMS substrate 140, and may also provide asealed, or hermetic, environment for the MEMS devices in the MEMSsubstrate 140.

In the CMOS-MEMS device 100, the vertical gap between the electrodes 121and the MEMS substrate 140 may be defined by the metal pads 123.Furthermore, the design rules for the electrodes 121 and metal pads 123may be tightened in this example because the electrode patterning is notperformed over the topography, but is instead patterned before theelectrode metal is deposited in the vias 219 and exposed regions 217.

FIGS. 2A-2G illustrate process steps in forming the device of FIG. 1with dual damascene electrodes, in accordance with an example embodimentof the disclosure. FIG. 2A illustrates the CMOS substrate 130 with thedielectric layers 101, 105, 109, 111, and 113 as well as the vias 103and the metal layer 107.

In an example embodiment, a dielectric layer 215 may be deposited on thedielectric layers 111 and 113. The dielectric layer 215 may comprise asilicon oxynitride, for example, although the disclosure is not solimited. The dielectric layer 215 may be utilized to pattern theelectrodes, so the material may be chosen to have the desired etch-stopcapability when subsequently thinning the formed electrodes. Inaddition, the thickness of the dielectric layer 215 may be utilized todefine a thickness of the electrodes above the dielectric layer 111.

FIG. 2B illustrates the dielectric layer 215 after patterning andetching, which thereby expose regions 217 where the electrodes are to beformed. Therefore, in an example scenario where the dielectric layers111 and 113 respectively comprise nitride and HDP oxide, a dielectricsuch as silicon oxynitride may be utilized for the dielectric layer 215where an etchant that removes silicon oxynitride while leaving the otherlayers intact is used.

FIG. 2C illustrates the forming of vias 219 in the dielectric layers 105and 111, where the vias 219 extend down to the metal layer 107. Aphotolithography process may be utilized to protect the top surface ofthe dielectric layers 111, 113, and 215 except where the vias are to beformed, after which the photoresist may be removed, resulting in thestructure shown in FIG. 2C.

FIG. 2D illustrates the forming of the dual damascene electrodes, wherea single metal layer is formed in the vias 219 and on the exposed topsurface of the dielectric layers 111 and 113. In an example scenario,the metal may be formed to be thicker than the dielectric layer 215 butthen thinned with a chemical-mechanical polish (CMP) process down to thethickness of the dielectric layer 215, demonstrating how this layer maybe utilized to define the electrode thickness adjacent to the vias 219.The metal for the electrodes 121 may comprise tungsten, for example, butother metals may be used depending on, for example, the desired workfunction, mechanical strength, and/or conductivity. For example, othermetals may comprise, but are not limited to, Titanium (TI), Tantalum(Ta), and copper (Cu).

The thickness of the metal as deposited may be thicker than, or extendabove, the dielectric layer 215, and then may be thinned back using aCMP process to be coplanar with the top of the dielectric layer 215.

FIG. 2E illustrates the process for forming metal pads 123 on theelectrodes, where dielectric layer 225 and a metal layer 223 may bedeposited on the top surface of the electrodes 121 and the dielectriclayer 215. The dielectric layer 225 may comprise a silicon oxynitride,for example, and the metal layer may comprise aluminum, for example,although the disclosure is not so limited as other dielectrics or metalsmay be used.

A photoresist layer may be deposited on the dielectric layer 225 and themetal layer 223 and the photoresist subsequently patterned to result inthe PR mask 227, thereby covering regions of the dielectric layer 225and metal layer 223 to protect them from the subsequent etch processesabove one or more of the electrodes 121.

A first etch process may be utilized to remove the exposed portion ofthe dielectric layer 225 and a second etch process may be utilized toremove exposed portions of the metal layer 223, followed by the removalof the PR mask 227, resulting in the structure shown in FIG. 2F where aportion of the dielectric layer 225 remains. The metal layer 223, theremaining portion of the dielectric layer 222, and the dielectric layer215 may then be removed, such as by wet chemical or dry etching, forexample, resulting in the metal pads 123 of FIG. 2G. A forming gasprocess may be utilized to anneal the remaining metal.

The structure shown in FIG. 2G represents the CMOS substrate 130 withthe metal pads 123 and dual damascene electrodes 121 that may then bebonded to a MEMS substrate resulting in the structure of FIG. 1.

FIG. 3 illustrates another example embodiment of a MEMS device with dualdamascene formed electrodes, in accordance with an example embodiment ofthe disclosure. Referring to FIG. 3, there is shown CMOS-MEMS device 300comprising CMOS substrate 330, MEMS substrate 340, and MEMS cover 350.The MEMS substrate 340 may be bonded to the MEMS cover 350 with a thindielectric film (such as silicon oxide, not shown) in between. In someembodiments, the MEMS substrate 340 comprises single crystal silicon orpoly crystal silicon, for example. The MEMS substrate 340 may beelectrically coupled to the CMOS substrate 330 via the metal layer 307.

The CMOS substrate 330 comprises a multi-layer structure, which maycomprise dielectric layers 301, 305, 309, 311, and 313. Conductive layer307 may comprise top metals for the CMOS substrate 330 and in an examplescenario, may comprise metal that was deposited on the surface of thedielectric layer 301 and the vias 303 and patterned to provideelectrical contact to various points on the CMOS substrate 330, therebyproviding isolated electrical connectivity to devices and circuits. Thevias 303 provide vertical electrical interconnects through thedielectric layer 301 between devices in the CMOS substrate 330 and themetal layer 307.

The dielectric layer 301 may comprise a passivation layer, for example,to protect and electrically isolate devices in the CMOS substrate 330,and may comprise silicon dioxide, silicon nitride, or similar material,for example. Similarly, the dielectric layer 305 is deposited over thedielectric layer 301 and the conductive layer 307. The dielectric layer305 may comprise silicon dioxide, for example, although other dielectricmaterials are possible, and may comprise a thicker dielectric layer thanthe other layers. In addition, the dielectric layer 309 may be on thedielectric layer 305, and may comprise silicon dioxide, for example. Thechoice of various dielectric layers may be made based on, for example,etch selectivity, density, and/or desired dielectric constant.

The dielectric layer 311 may comprise a nitride material, for example,although the disclosure is not so limited, and may provide a surface onwhich the electrodes 321 are formed. The electrodes 321 may comprise asingle metal layer formed in a dual damascene process extending from themetal layer 307 to the top surface of the dielectric layer 311.

In an example scenario, a different dielectric material from thedielectric layer 311 may be used for the dielectric layer 313. Forexample, the dielectric layer 313 may comprise a high density plasma(HDP) oxide layer adjacent to the dielectric layer 311.

The example embodiment shown in FIG. 3 may be similar to that shown inFIG. 1 with the dual damascene electrodes 321, but with the gaps betweenelectrodes 321 and the MEMS substrate 340 being configured by the CMOSsubstrate 330 as opposed to the MEMS substrate, as illustrated in FIG.1.

For example, a wider gap between the CMOS substrate 330 and the MEMSsubstrate 340 is enabled by the cavity 331 formed in the CMOS substrate330 and a narrower gap results from the distance between the electrodes321 and the MEMS substrate 340, whereas in FIG. 1, narrower gaps areprovided by the standoffs 143 in the MEMS substrate 140 and wide gapsare in regions where there are no standoffs 143.

The MEMS substrate 340 may comprise a structural layer and a devicelayer, where the structural layer comprises the movable structures andthe device layer comprises the electronic devices or functionality forthe movable structures. The MEMS cover 350 may comprise a protectivestructure for the MEMS substrate 340, and may also provide a sealed, orhermetic, environment for the MEMS devices in the MEMS substrate 340.

FIGS. 4A-4D illustrate process steps in forming the device of FIG. 3with dual damascene electrodes, in accordance with an example embodimentof the disclosure. FIG. 4A illustrates the CMOS substrate 330 with thedielectric layers 301, 305, 309, 311, and 313 as well as the vias 303and the metal layer 307.

In an example embodiment, a dielectric layer 415 may be deposited on thedielectric layers 311 and 313. The dielectric layer 415 may comprise asilicon oxynitride, for example, although the disclosure is not solimited. The dielectric layer 415 may be utilized to pattern the dualdamascene electrodes, so the material may be chosen to have the desiredetch-stop capability when the formed electrodes are subsequentlythinned. In addition, the thickness of the dielectric layer 415 may beutilized to define a thickness of the electrodes above the dielectriclayer 311.

FIG. 4B illustrates the resulting structure after trench patterning thedielectric layer 415, etching vias in the dielectric layers 305 and 311that extend down to the metal layer 107, and forming of the dualdamascene electrodes. The electrodes may be formed by applying a singlemetal layer in the vias and on the exposed top surface of the dielectriclayer 311. In an example scenario, the metal may be formed to be thickerthan the dielectric layer 415 but then thinned with achemical-mechanical polish (CMP) process down to the thickness of thedielectric layer 415, demonstrating how this layer may be utilized todefine the electrode thickness adjacent to the vias. The metal for theelectrodes 321 may comprise tungsten, for example, but other metals maybe used depending on the desired work function, mechanical strength,and/or conductivity.

The thickness of the metal as deposited may be thicker than, or extendabove, the dielectric layer 415, and then may be thinned back using aCMP process to be coplanar with the top of the dielectric layer 415.

FIG. 4C illustrates the process for forming cavity 331, where aphotoresist layer may be deposited on the electrodes 321 and thedielectric layer 415 and subsequently patterned to result in the PR mask425, thereby covering the electrodes 321 and a portion of the dielectriclayer 415 to protect them from the subsequent etch processes whileexposing a region 419 for the cavity 331.

One or more etch processes may be utilized to remove the exposed portionof the dielectric layers 415, 311, 309, and 305 in the exposed region419, followed by the removal of the PR mask 425 and the remainingdielectric layer 415, resulting in the structure shown in FIG. 4D.

The structure shown in FIG. 4D represents the CMOS substrate 330 withcavity 331 for wider gap separation between the CMOS substrate 330 andthe MEMS substrate 340, and the dual damascene electrodes 321 exhibitnarrower gap separation when bonded to the MEMS substrate 340.

In an example embodiment, a system is disclosed for MEMS devices withdual damascene formed electrodes. In this regard, aspects of thedisclosure may comprise a complementary metal oxide semiconductor (CMOS)substrate comprising: a conductive layer; a first dielectric layercovering at least a portion of the conductive layer; a second dielectriclayer above the first dielectric layer; a dual damascene electrodecomprising a single metal layer on a top surface of the seconddielectric layer and extending through the second dielectric layer and aportion of the first dielectric layer to the conductive layer; and ametal pad above the second dielectric layer. A MEMS substrate may becoupled to the CMOS substrate via the metal pad, where the MEMSsubstrate comprises standoffs extending from a first surface of the MEMSsubstrate. A MEMS cover may be coupled to a second surface of the MEMSsubstrate opposite to the first surface. A metal pad may be on at leastone electrode and the MEMS substrate may be electrically coupled to theCMOS substrate via the metal pad, the at least one electrode, and theconductive layer.

In another example embodiment, a system is disclosed for MEMS deviceswith dual damascene formed electrodes. In this regard, aspects of thedisclosure may comprise a complementary metal oxide semiconductor (CMOS)substrate comprising: a conductive layer; a first dielectric layercovering at least a portion of the conductive layer; a second dielectriclayer above the first dielectric layer; a dual damascene electrodecomprising a single metal layer on a top surface of the seconddielectric layer and extending through the second dielectric layer and aportion of the first dielectric layer to the conductive layer; and acavity in the first and second dielectric layers extending to theconductive layer. A MEMS substrate may be coupled to the CMOS substratevia the conductive layer and a MEMS cover may be coupled to the MEMSsubstrate on a surface opposite to a surface of the MEMS substratecoupled to the CMOS substrate. The MEMS substrate may be electricallycoupled to the metal layer.

As utilized herein the terms “circuits” and “circuitry” refer tophysical electronic components (i.e. hardware) and any software and/orfirmware (“code”) which may configure the hardware, be executed by thehardware, and or otherwise be associated with the hardware. As usedherein, for example, a particular processor and memory may comprise afirst “circuit” when executing a first one or more lines of code and maycomprise a second “circuit” when executing a second one or more lines ofcode. As utilized herein, “and/or” means any one or more of the items inthe list joined by “and/or”. As an example, “x and/or y” means anyelement of the three-element set {(x), (y), (x, y)}. In other words, “xand/or y” means “one or both of x and y”. As another example, “x, y,and/or z” means any element of the seven-element set {(x), (y), (z), (x,y), (x, z), (y, z), (x, y, z)}. In other words, “x, y and/or z” means“one or more of x, y and z”. As utilized herein, the term “exemplary”means serving as a non-limiting example, instance, or illustration. Asutilized herein, the terms “e.g.,” and “for example” set off lists ofone or more non-limiting examples, instances, or illustrations. Asutilized herein, circuitry or a device is “operable” to perform afunction whenever the circuitry or device comprises the necessaryhardware and code (if any is necessary) to perform the function,regardless of whether performance of the function is disabled or notenabled (e.g., by a user-configurable setting, factory trim, etc.).

While the disclosure has been described with reference to certainembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted withoutdeparting from the scope of the present disclosure. In addition, manymodifications may be made to adapt a particular situation or material tothe teachings of the present disclosure without departing from itsscope. Therefore, it is intended that the present disclosure not belimited to the particular embodiments disclosed, but that the presentdisclosure will include all embodiments falling within the scope of theappended claims.

What is claimed is:
 1. A microelectromechanical system (MEMS) devicecomprising: a complementary metal oxide semiconductor (CMOS) substratecomprising: a conductive layer; a first dielectric layer covering atleast a portion of the conductive layer; a second dielectric layer abovethe first dielectric layer; a dual damascene electrode comprising asingle metal layer on a top surface of the second dielectric layer andextending through the second dielectric layer and a portion of the firstdielectric layer to the conductive layer; and a metal pad above thesecond dielectric layer; a MEMS substrate coupled to the CMOS substratevia the metal pad, the MEMS substrate comprising standoffs extendingfrom a first surface of the MEMS substrate; and a MEMS cover coupled toa second surface of the MEMS substrate opposite to the first surface. 2.The MEMS device of claim 1, wherein a metal pad is on at least oneelectrode.
 3. The MEMS device of claim 2, wherein the MEMS substrate iselectrically coupled to the CMOS substrate via the metal pad.
 4. TheMEMS device of claim 1, wherein the MEMS substrate is electricallycoupled to the CMOS substrate via the at least one electrode and theconductive layer.
 5. A microelectromechanical system (MEMS) devicecomprising: a complementary metal oxide semiconductor (CMOS) substratecomprising: a conductive layer; a first dielectric layer covering atleast a portion of the conductive layer; a second dielectric layer abovethe first dielectric layer; a dual damascene electrode comprising asingle metal layer on a top surface of the second dielectric layer andextending through the second dielectric layer and a portion of the firstdielectric layer to the conductive layer; and a cavity in the first andsecond dielectric layers extending to the conductive layer; a MEMSsubstrate coupled to the CMOS substrate via the conductive layer; and aMEMS cover coupled to the MEMS substrate on a surface opposite to asurface of the MEMS substrate coupled to the CMOS substrate.
 6. The MEMSdevice of claim 5, wherein the MEMS substrate is electrically coupled tothe metal layer.